RB951Ui-2HnD port 5 not getting 100 mbps connection

Hardware MikroTik hardware general
1

Hello there.

I’m using a RB951Ui-2HnD as my main router on my home network. I have a TP-Link TL-WR1043ND running OpenWRT upstairs with DHCP disabled to expand the range of the WiFi and connect some wired equipment.

I use a 15 m long CAT6 cable to connect both “routers” (the TP-Link is just acting as an extender) with CAT5 connectors (making it suitable for 100 mbps, correct?) on both ends.

I tried using the port 5 of the RB951Ui-2HnD, because eventually I might want to use the PoE feature of this port. According to the log, the link between them starts at 100 mbps, then the connection goes down, and comes back at 10 mbps. I’ve tried a few times, with the same results.

Then I tried changing the port of the Mikrotik, and on port 4 I get a 100 mbps link, according to the log, and it doesn’t go down (maybe only once, and immediately comes back again). I thought the problem laid on the cable, but since I can get a 100 mbps connection using port 4, I’m thinking the problem might be on my Routerboard. Unless for some reason port 5 requires a better cable to get a steady 100 mbps link (that’s something I’m going to try, using a pre-built, shorter cable to connect the routers to check how they react.

I don’t know if this is relevant, but I’m using a straight cable instead of a crossover one.

What might the problem be in this case?

2

No one? :confused:

3

As you said, port 5 on the 951Ui is the PoE-out port. It might be interesting to have you try disabling PoE-out entirely on that port and see if that manages to change anything. I know that you said eventually you might want to use the PoE out feature, but just as an experiment, try turning it off (default setting, I believe, is “auto”).

My personal experience has been that when I actually try to use it as a PoE out port with a PoE-capable device, for whatever reason, the very first time I use it as a PoE power source, I have wonky results UNTIL I reboot the router, and then after that, everything is fine from that point forward. One time, I booted up a 951Ui for the first time, plugged another 951Ui into port 5 (for both data and power), and it would refuse to link at anything other than 10Mbit/s. I tried rebooting the second 951Ui, forcing both devices to 100Mbit/s, changing the ethernet cable I was using, etc. Nothing worked. Then I rebooted the main 951Ui, and after it booted up, everything worked perfectly. (Try physically unplugging the power from the 951Ui, not just issuing a software “reboot” command.)

– Nathan